Helicopter rotor



June 30-, 1953 1. SIKORSKY 2,643,724

HELICOPTER ROTOR Filed Feb. 21, 1947 3 Sheets-Sheet 1 I 140 AUTOROTATIONNORMAL Q. POSITION A POWER-ON neon l. SIKORSKY NVENTOR ATTORNEY June 30,1953 l. 1. SIKORSKY HELICOPTER ROTOR 3 Sheets-Sheet. 2

Filed Feb. 21, 1947 IGOR I. SIKORSKY INVENTOR ATTORNEY June 30, 1953 l.l. SIKORSKY 3,

HELICOPTER ROTOR Filed Feb. 21, 1947 $.Shaets-Sheet :5

IGOR IQSI'KORSKY INVENTOR M KM ATTORNEY Patented June 30, 1953 UNITED:STATES PATENT OFFICE HELICOPTER noTo-R f Igor .I. Sikorsky, Bridgeport,Conn., assignor to United Aircraft Corporation, East Hartford, Conm, acorporation of Dela-ware Application 'February21, 1947, Serial No.730,049

1 This invention relates generally to improvemen-ts in rotary wingaircraft; and more particularly to improved control mechanism, wherewithcertain control functions presently performed manually are performedmechanically and instantaneously, and wherewith aerodynamic damping isrendered available without-loss of stability orsafety the aircraft; andspecifically to improved automatic pitch control mechanism responsive totorque requirements of the lifting rotor, or rotors.

It has been found that the torque requirements of .a helicopter rotorbear a definite relationship to the lift of the rotor and also to thetorque capacity of an internal combustion engine of the type commonly:used in aircraft. Further, it has been found that the ratio of theangle ofincidence of a rotor blade to the torque required to turn theblade at different angles of incidence is'substantiallya linear functionwithin limits useful in helicopters. Inasmuch as'the spring rate .oftorsion springs is substantially linear within the normal operatingrange ofsuch springs, it is now found possible to balance with suchsprings, or the like, the linearly variable torque between the engineand-the rotor to obtain a substantially self -contained, automaticallybalanced'pitch control mechanism for helicopter lifting-rotors.

Automatic aerodynamic damping has also been long recognizedas desirablein helicopters; How' ever, with presently known structures havingautomatic control of the pitch. of the lifting rotors upon applicationof torque, the pitch-must in crease with the increase of torque. Theoperation :is generally as follows: As more torque is applied, the bladedrags back around the vertical hinge, and'the pitch increases, and .astorque is reduced the blade moves ahead about the drag hinge and thepitch decreases. This result may be produced by a variety of means suchas real inclined drag hinges, or by virtual inclination of hinges (i.e., the hinge itself, is vertical but the controls are so joined that asthe blade moves about the drag hinge the pitch changing linkage operatesto change the blade pitch, for example).

With the above in mind, it can 'be readily observed that the direction.of pitch change for response to torque, which is in proportion to dragof the blades, is exactly opposite tothe pitch change required foraerodynamic dam-ping. "For natural aerodynamic damping and stabilityitis desirable to have the blade decrease its pitch as it lags hack andincrease its pitch as it moves forward. 'This principle has often beensuggested 13 Claimslcl. iron-135.72)

but it cannot actually be applied to a helicopter However, bysimplifying the controls-013a heli copter by the elimination of thetotal pitch control, it is possible to obtain synchronous and automaticoperation of the main pitch of the rotors upon movement of the throttle.This will eliminate one contro'land make the helicopter the easiest andsafest type of aircraft to operate.

Heretofore, it has been common practice, as-

deseribed in my patents, Nos. 2,318,259 and 2,318,260, to manuallyoperate a main pitch control and to have the engine throttlesynchronized with the main pitch. This method, it is'believed, has beenused on all production helicopters, to date. This type of control hasrequired the use of both hands of the pilot in take-off and othermaneuvers and has made it difficult for the pilot to operate the radio,hydraulic hoist and other devices which require separate controls. With"the present device, the pilot can set thethrottle for any desired engineoutput and be concerned" with the cyclic control, or joystick, only.Furthermore, this type of throttle could easily be of the foot pedal tye, or, :if necessary, it could be mounted on the joystick for operationby the same hand which operated the cyclic controls.

My improved structure includes an adjustable connection in the .driveshaft of a helicopter, which connection responds to torque of theengineor rotor to change the pitch of the rotor in a y direction to absorb thefull power of the engine.

Thus, when the engine throttle is opened, the

increase in power will increase the pitch of the rotor blades insubstantially exact proportion to absorb the full torque output,'and theenginerotor system can be adjusted to maintain the optimum fuelefiiciency during power operation. In the event of power failure, aspring mechanism, or equivalent, will operate instantly to move all therotor blades of the rotor simultaneously to theauto-rotative attitudewithout the requireprovide improved automatic mechanism for controllingthe pitch of a rotor for rotary wing aircraft.

Another object is to provide an improved rotor drive and control systemwherewith aerodynamic damping is used, and the structure for obtainingthe same.

A further object is to simplify and reduce the number of controls of ahelicopter to the same number and type of controls that are common onfixed wing aircraft; namely, a joystick, rudder pedalsandthrottle, and atrimming device.

Other objects, features and advantages reside in the details ofconstruction and the arrangement of parts, and will be either pointedout or obvious in the following specification and claims.

- In the-drawings,

Fig. 1 is a diagrammatic view of parts arranged to illustrate thefunction of the invention;

Fig. 2 is a diagrammatic perspective view of a presently preferred formof the invention;

Fig. 3 is a partial plan diagrammatic view of Fi 2; e

Fig. 4 is a detailed partial sectional View of a control jack; r

Fig. 5 is adetail elevational view, with parts in section, of theyieldable torque responsive portion of the drive shaft;

Fig.6 is a detailed side view of a dual purpos throttle and pitchcontrol stick;and

Fig. 7 is, a modification of the throttle and pitch stick;

Referring to Fig. 1, an air cooled engine it) drives a rotor blade '20through an overrunning clutch contained within the rotating housing 12.A fan I4 is mounted on the periphery of housing 12 to direct cooling airover' the engine. On the upper portion of the housing I2 is splinedconnection 15 for driving torque responsive member I6 which in turnrotatesan upper axially fixed drive shaft [8 that is connected to thevariable pitch rotor blade through. drag and flapping hinges (notshown). The pitch of the rotor blade 20 is controlled in the arrangementshown in Fig. l by a control horn 26 which connects with a push-pull rod23 connected to a tilt plate mecha nism. The tilt plate mechanism 30 ismade up of a pair of relatively rotatable members 32 and 34. The member32'is connected with the drive shaft I8 through a universal joint (notshown) and rotates therewith. The member 34 may be main:

tained non-rotatable with a suitable connection to the helicopterfuselage (not shown). The members 32 and 34 may be connected togetherfor conjoint tilting or up and down movement by ball bearings interposedtherebetween in any conventional manner. I

The tilt plate mechanism 301 may be moved up and down by a plurality ofpush-pull rods 40, only one of which is shown. The rod connects by apivot at its upper end to the member 34 and at its lower end by a pivotto a floating link 42 at some pointbetween the ends of the link 42,

which point may be best determined by particular requirements indifferent ships.

The left hand end of the floating link 42 may be moved up and down bycables 44 suitably guided upon pulleys by means of a manual pitchcontrol lever 46 which is in the cockpit of the helicopter. The lever 46may be used in this invention for trimming the controls which areoperated automatically and now to be described.

A throttle control 50, adjacent the pilots seat,

- connects through links 5|, 52 to a throttle valve -arm 53-oncarburetor 54 which meters the fuel charge'to intake manifold 56 on theengine H). 'An increase inthe airfuel mixture to the engine will causea'corresp'o'nding increase in the horsepower output which will tend toincrease the speed of the rotor. However, an increase in speed causes anincrease in drag and therefore the increased horsepower increases thetorque absorbed by the rotor. The increase in torque acts through thetorque responsive member 16 to increase the pitch ofthe blades, in amanner now to be described,

which in turn will tend to stabilize the speed of the rotor.

The drive connection I 5 has internal straightsplines 69. which matewith the straight splines associated with the spiral splines may bereducedby substituting ball races for the-splines if desired.

Upward motion of the member I6 is resisted. by a compression. spring 68carried between a rod 10 and a portion of the fuselage 12. The. arm 1ais pivotally mountedzupon a pin 14 which is carried upon bearingssurrounding the member Ilito permit relativerotation between the arm 10and the member [6 but connecting the two for axial movement together.The right hand end of;

the arm 10 is carried in a sling-16' which is pivoted by differentadjustment holes upon the'arm 10. With such adjustment it is possible tochange both the leverage of the arm 10 and its position of control toprovide for pitch adjustment between the rotor blades and' the engine.-

in' aerodynamic characteristics, and to the nor-.

mal variation between production engines.

Vertical movements of the arm 70- in response to torque cause up anddown movements of the push-pull rod 82.that is connected to the floatinglink 42 at its upper end. Accordingly, it is seen that with a change intorque of the engine H.) the" pin 14 will be moved up and down to rockthe arm '70 around its pivot point 80 against the bias of the spring 63to raise or lower the tilt mechanism. 30 to change the pitch and hencethe lift of the blade 28. It will thus be evident that link: 42comprises a differential element movable to vary the collective pitch ofthe rotor blades as a result of movement of lever 46 or torquerespom'sive arm 10..

Referring'now to Fig. 2, pivot mounts for the blade 20 and a slightlymodified control mecha-- nism are shown, which structure performssubstantially the same function as that mechanism:

described in connectionlwith Fig. 1. The blade 20 is mounted upona spar22 which inturn is Inthis way, the system may-be adapted to sets ofbladesthat may have different airfoils and thusdiffer mounted upon adrag hinge 90 that permits the blade to have lag-lead (hunting)movements initsplane of rotation as it rotates. A flapping hinge 92permits the blade 20 to flap and cone in response to aerodynamic andcentrifugal forces as itrotates. The shaft I8 extends downwardly througha suitable gearreduction mechanism 94 to a torque responsive mechanism II6.

' Axial movement iofthe rotating swash plate I32 in response to manualor automatic controls will act through the push-pull rod I28 to rotatetorque tube I30, mounted in'bearings I36, I38 to rotate crank IIlI.Movement of crank IBI will act through push-pull rod I90 to rotatecontrol horn 9B which is connected to the spar 22 and will move blade2!] in a pitch increasing or pitch decreasing direction. The spar 22 hasinternal radial thrust hearings to permit of pitch change, and fordetails of construction thereof reference may! be had to Patent No.2,529,635, issued November 14, 1950.

As the blade 2llmoves back and forth around the pivot 90; as indicatedby the arrow 98, Fig.3, push-pull rod 506 will rotate about a ball jointI02 at its upper end in a direction to vary the pitch of the blade 20 byrocking the rod I00 around a second ball joint I84 on the lower end ofthe rod I69. Motion to the right of the blade 20 will cause the ball I82to swing downwardly on an arc underneath the ball joint Hi2 which willcause a decrease in pitch of the blade 20. Inasmuch as such laggingmovement is usually due to excess drag of the blade 28, the decreasedpitch will cause a reduction in drag and hence permit the blade to moveforwardly again under the influence of centrifugal force. tions to theleft (i. e., in thedirection of rotation of the rotor) willcause anopposite rotation of the push-pull rod I02 and cause a pitch increase ofthe blade 2!! and hence an increase in drag.

The above action is conveniently called aerodynamic damping because agivenmotion causes an aerodynamic change in action of the part moved inthe air in a manner to correct for a disturbing force. When the blademoves forward into the auto-rotative position (shown in dotted line inFig. 3) the pitch increase due to the aerodynamic damping function willbe of small magnitude. and will be offset and overriden by the pitchdecrease caused by the torque 'responsive mechanism. 1

The axial movement of the swash plate I32 is transmitted thereto by thestationary swash plate I34. Theposition of swash plate I34 is controlledthrough jackscrews Mil, the details of which form .no part of thisinvention but may be seen in the above-mentioned U. S. Patent No.

2,529,635, which move up and down in response to rotation of thesprockets 42 and I43 by means of the chain HM. As shown here, thechainand sprocket arrangement controlling the jackscrews I controls onlythe total pitch of the blades. For the sake of clarity, the chain andsprocket controls for'cyclic pitch have been omitted but maybe of thetype shown in the aforementioned patent. Movement of the chain I46 bymeans of manual controls will act through the sprocket and worm device2% to rotate the sprocket M2 on the upper end thereof. Rotation ofsprocket [42- will rotate sprockets; I43 to raise or lowerswash platesI32, I 34 axially ofshaft I8 to change the pitch of the blade 20. V

The sprocket and worm device 290 is mounted on a stationary partof thehelicopter such as the plate 204 and has a sp'rocketZiiG on .the outsideBlade mo-- of the lower portion thereof. Rotation of the:

sprocket I42 on the upper end of the control jack 200. may also beobtained through vertical movement of the rod 202 which is connected toa tubular member 2M (see Fig. 4) throughbearings 203. outer casing 208.The casing 208 has internal straight splines 2i0 engaging the splines2I2 which are integral with the tubular member.

2 M. Mounted in bearings 2 I6 is an outer tubular member 2I8 which hassprocket M2 on its upper end. On the inside of the tubular member 2I8are half ball races 220 for a number of revolutions which cooperate withhalf ball races 222 out in the outer surface of the tubular member 2M.

crease the friction in this device. On the outside of the tubular member2I8 is a ball return 223 extending from tap hole 224 to tap hole 225.

The ball race 225 on external member 2 I8 is only The ball out betweenthe tap holes 224 and 228. return 223 serves to return the ball bearingsfrom. hole 224 to hole 226 as the balls are forced out of hole 224 as aconsequence of movement of the tubular members and vice versa when themovement of the tubular members is in the opposite sense. The pitch ofthe ball races is such that rotation of the casing 208 will act through.

the splines 2H 2I2 to rotate the inner tubular member 2| 4 andconsequently rotate the outer.

It is apparent, therefore, that movement of the chain I46 through manualpitch control means operated by the pilot would act through splines 2m,2I2 to rotate the tubular members 2M, 2I8 conjointly and thereforerotate the sprocket I42 to change the pitch of the blade 20. It willalso be apparent that axial movement of the rod 202 in response to thetorque applied to the blades will act to rotate the tubular member 2I8and sprocket I82 for pitch changing movement of the blade. in Fig. 2 isthe equivalent of the differentialelement' 42 in Fig. 1. v

The vertical movement of the rod 292 is a result of an increase ordecrease in the torque transmitted through the torque responsive de-'vice IIB. As the device IIG moves vertically in response to torque, themovement is transmitted through pins I'M to the arms I'Iii which areconnected at one end to rod 202 and at the other end to sling ITS whichis pivoted on a stationary part of the helicopter. The arm Ill and'thesling I76 have various adjustment holes which serve to adapt the systemto various conditions.

As may be seenin Fig. 5, the housing I2 containing'the over-runningclutch,. the details of member 306 has splines 308which engage splines3H] on the composite member 3! 2 and is held against axial movement withrespect to the com- The sprocket 266 is integral withthe.

Cooperating with and completely filling the" ball races 220 are ballbearings which greatly de-- Thus the sprocket and worm device 200' 7,posite member 312 by means of lock nut 314 on the bottom of compositemember 3 i 2 which holds the intermediate member 306 in contact withbearing 316. The-bearing 316 is provided to permit arms 1'10 to remainstationary while the composite member 312 rotates. A dust and oil seal315 is provided between the top of casing 300 and intermediate member306 and permits sliding movement between the parts. Thus it may be seenthat the splined drive connection aifords a convenient assembly ofrelatively simple parts.

The composite member 312 is fabricated by means of welds from a numberof parts which permit of easy construction. The member 312 drives anannular member 322 which has spiral splines 324 on the upper innersurface thereof. Engaging these spiral splines 324 are cooperatingspiral splines 326 on member 328. The member 328 drives shaft 18 and isconnected therewith by means of a keyed connection 3H1. It will beevident that power is transmitted from annular member 300 to shaft 13through the intermediate splined member 306, composite member 312, andthence to member 322 where the internal spiral splines 324 cooperatewith and drive the splines 326 on the member 328.

Obviously, if a resistance force were not provided, the spiral splineswould ride up on splines 326 to the full limit. Compression springs 330are provided for this purpose and are held in place by means of members332, 334. The member 332 is mounted upon bearings 336 and member 334bears against member 336. Lubrication for the bearing 338 is suppliedthrough the lubricating wick 340, one end of which is immersed as isbearing 336 in a suitable supply of oil, not shown. Since the members332, 334 are mounted in bearings in this fashion the upper ends of thesprings 330 will not rotate relative to the lower ends. Between the topof annular member 322 and member 328 is a slidab-le dust and oil seal342.

When the torque transmitted through member 116 is increased, theinternal spiral splines 324 will ride upon the external spiral splines326 on member 328. Since the splines 302, 304 in the lower portion arestraight, such axial movement is possible. However, the compressionsprings 330 will resist any upward movement of the spiral splines. Aspointed out hereinbefore, the torque absorbed in the rotor bears adefinite relationship to the lift of the rotor and to the torque of aninternal combustion engine. Therefore, the axial movement of the torqueresponsive device 116 may be utilized as a measure of the required pitchangle, and isconveniently transmitted by means of pins 114 and arms 110to the rod 202 to vary the pitch of the blade 20 as the torque isvaried.

Should the friction in the spiral splines reach an undesirable value, itmay be reduced by any of the well-known expedients. For example,cooperating half ball races or a cam and roller may be used and, in thelatter instance, the contour of the cam track may be varied to vary theoperating characteristics of the torque responsive member where desired.

The diagrammatic representation of my invention in Fig. 1 shows separatecontrol sticks for total pitch and throttle. These controls, however,may conveniently be combined into one dual purpose stick which serves tocontrol the throttle or pitch as shown in Figs. 6 and 7.

Fig. 6 shows a control arm 400 which is pivoted about two pivots 402,403. On the periphery of the pivot 402 are inclined surfaces.

the outside member 404 are spring biased ball bearings which normallywedge between the outer member 404 and the inclined surfaces. As may beseen in the drawing, the internal shaft 406 has portions 400, integraltherewith, interposed between pairs. of the spring biased ball bearings.A loose fit allows slight movement of portions 406, and the end of shaft406 near the pivot is an arouate path having the pivot as a center. Thisslight movement suflicient, however, to dislodge the balls which arewedged between the inclined surfaces and the inside surfaces of member404. It will now be apparent that force applied at knob 410 on the outerend of shaft 406 will move the other end of shaft 406 and portions 408to dislodge the balls and permit rotation about pivot 402. However,should the arm 400 be grasped in the region denoted by numeral 412, theball bearings will remain wedged between the pivot 402 and the outermember 404. When this condition obtains, rotation will be about thepivot 403.

Offset from the pivot 402 is a connection to throttle cable 414 whichcontrols the position of the throttle arm on the carburetor. It shouldbe noted that cable 414 passes through the axis of pivot 403. Therefore,when rotation is about pivot 403 there will be no change in the'throttlesetting. Pitch control cable around a pulley 416 which is adapted forrotation around pivot 403 when stick 400 is rotated thereabout. Thepitch cable 144 is connected to chain 146 to rotate the lower sprocketin the sprocket and worm device 200 (Fi 2).

In operation, the pilot may control the throttle separately by movingthe knob 410 to cause rotation of the arm 400 about the pivot point 402.Through the torque responsive device (described supra) an increase ordecrease in the throttle, causing an increase or decrease in torque,will act to change the pitch of the blade 20. However, should the pilotdesire to trim the pitch, he may do so by grasping the arm 400 in theregion 412 to cause rotation about the pivot 403.

Fig. '7 shows another method of making a dual purpose control stick. Inthis modification, an arm 450 is pivoted at one end about point 452 andhas at its other end a pivot 454. Mounted on pivot 454 is an arm 456. Ifthe pilot should grasp the arm 456 in the region 458, the force wouldall be transmitted directly through the pivot 454 so that there will beno rotation about pivot 454 but there will be rotation about the pivot452. However, if the force should be applied at 460 there will be amoment arm about the pivot 454 and the rotation will be about this pivotonly.

A throttle control cable 462 is attached to 2. depending portion of thearm 456 and passes through the axis of pivot 452. The pitch controlcable 144 rides on pulley 464 which is adapted to rotate about pivot 452conjointly with the arm 450. The pilot may vary the pitch by applyingforcein the region 458 which will allow rotation about the pivot 452 andconsequently move the pitch control cable 144. The throttle may beadjusted by applying force in the region 460 which will cause therotation to be about the pivot point 454 and move the throttle cable462.

Operation Under all normal conditions the pilot need con- Be-' tween theinclined surfaces on the pivot 402 and 144 is wrapped" cern himself onlywith throttle setting? setting thethro-ttle-in a given position, thetorque applied hr therotor blades through the torque responsive-devicetlfi will assume a value consistent with thecharacteristics ofthe-particular rotor'ntilized. Should the' throttl ebe-incrasefc l' fromthis -position, th -tOrque tranS- mitted -wil'l be correspondingrncreasedw The increase-in: torque-will cause' 'tl ride upon the spiralsplines aiifi to ari' 'amou'nt determined by the characteristics of thecompression springs; atil flfhis ward motion of the torque responsivedevice I, ll' be transmitted to arms" I18 through pins" PM and willcause the ro d 202 tomove-upwa r' The-vertical movement of therodf2-II2- will-beftransniitted into rotational movement of the"outer"tubular -memberjfflj of the controljack Eli-throughth'eball rac sm, 222. The rotation of the outer tubular member 2I8 will rotatesprocket M2 which engages chain I44; and will, therefore, rotate all theother sprockets Hi2 a corresponding amount. This rotation of thesprockets 542 will act through jackscrews I49 to move the stationaryswash plate I34 and the rotary swash plate I32 upwardly to cause anincrease in the pitch of the blade 20. Thus it may be seen that anincrease in the throttle setting will cause a corresponding increase inthe pitch of the rotor blade.

Should the throttle setting now be decreased, the compression springs330 will force the splines 324 downwardly with respect to the spiralsplines 326. This downward motion will be transmitted through the armsIII) to the rod 202 which will also be moved downwardly. The downwardmotion of the rod 202 will act through the control jack 200 to rotate thchain I44 in an opposite direction to increase the pitch in an amountcorresponding to the decrease in throttle.

Under all operating conditions (both power-on and power-off orauto-rotative conditions) the aerodynamic damping function will obtain.As the blade 20 hunts about the drag hinge 9B the pitch will beautomatically varied in accordance with the desired condition. When theblade moves to the left (as viewed in Fig. 3) the relative position ofpivot points I02 and I04 will be changed so as to move the control horn96 upwardly to increase the pitch of the blade. As the blade drags backor moves to the right, the control horn 96 will be moved downwardly todecrease the pitch of the blade 20. Thus, it may be seen that if theblade drags back due to increased drag, th pitch of the blade will bedecreased and will cause a consequent decrease in the drag of the bladeand permit the blade to return to a normal position. When the blademoves to the left or leads, the-pitch of the blade will be increased tocause the drag to be increased and the blade to return to a normalcondition.

The required changes in pitch to attain aerodynamic damping as set forthabove are of small degree when compared to the pitch changes requiredfor the various operating conditions which will be imposed upon theblade in accordance with the torque transmitted through the torqueresponsive device IIB. Should the engine fail, the blades would moveforward into the auto-rotative or power-off position. Due to the offsetposition of the pivot points I02, I04 the pitch of the blades would beincreased. Such an increase in pitch would be very undesirable since itis required that the blade be in a lower pitch setting in operatingunder auto-rotative conditions. However, when the engine fails, theoverrunning clutchv contained" within housing I 2 permits the blades to:continue-to rotate buts-there will. no longer be any torque: transmittedthrough the torque responsive 'device LIE! Under vthese conditionsthecompression springs will move the spiral splines: 324-tontheirliowermostposition and consequently moveaarmgiflfland rod 2&2 to .theirlowermost positions? *EThfis J war act: through the control jack 20 0andl thepitch: mechanismtodecrease the: pitch of theblades-3Sincathepitch change in responseito the :t'orqne. is greaterthan the: pitch changes-in response to the. aero-.-. dynamic dampingfunction, the net result will be a material decrease in the pitch of theblades. Thus' itmay be seenthat in addition to providing automaticcontrols fora helicopter and aerodynamic dampfng of the blades, 1 haveprovided a safer e icepte ,1.

Should the pilot desire totrim th pitch set.- ting iinppsed on thebladebythe automatic: on: trols,"or 'shoul-d-hedesire to modi'fythe'pitch of the blade in order to perform some abnormal maneuver,manual'pitch control means are provided which may override and modifythe setting imposed by the automatic control;

It is tobe understood that th invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherWays without departure from its spirit as defined, by the followingclaim-s.

I claim:

1. In a, helicopter, in combination, an engine driven shaft, a, rotordrive shaft, a blade pivotally mounted on said drive shaft for laggingand leading movements'in th plane of its rotation and for pitch changes,a blade pitch changing horn on said blade, torque responsive meansconnecting said shafts, means for increasing blade pitch upon torqueincrease and decreasing blade pitch upon torque decrease toward anoptimum auto-rotational no-torque pitch including linkage meansoperatively connecting said torque responsive means with said bladehorn, said linkage means also including means for decreasing the pitchof said blade as the latter lags back in its plane of rotation and forincreasing the pitch thereof as said blade moves forward.

2. In a helicopter, an engine having control means therefor, a driveshaft, a variable pitch blade mounted on said drive shaft for lag-leadmovements, pitch control means connected to said blade and includingtherein means for decreasing the pitch of said blade when lagging andincreasing the pitch of said blade when leading, torque responsive meansincluding an element in said shaft for providing movement of saidelement in response to chang in torque, a. composite stick having apivoted end and a free end, a pivot between said ends providing apivoted end portion, manual means for selectively moving said stickbodily about its pivoted end for controlling said pitch control means orfor moving the pivoted end portion only thereof about said intermediatepivot, linkage means for connecting said engine control means with saidpivoted end 1 portion, and means connected to said pitch control meanfor moving the latter in responseboth to bodily movement of said controlstick and movement of said torque responsive means.

3. In a helicopter, an engine having control means therefor, a driveshaft, a variable pitch blad mounted on said drive shaft for lag-leadmovements, pitch control means connected to said blade, torqueresponsive means including an element in said shaft for providingmovement of means.

said element in response to change in torque, a composite stick havinga, pivoted end and a free end, apivot between said nds providing apivoted end portion, manual means for selectively moving said stickbodily about its pivoted end for controlling said pitch control means orfor moving the pivoted end portion only thereof about said intermediatepivot, linkage means'for connecting said engine control means with saidpivoted end portion, and means connected to said pitch control mean formoving the latter in response both to bodily movement of said controlstick and movement of said torque responsive IGOR I. SIKORSKY.

Name Date Number Vawter June v16, 1908 Number Number Name Date Bard Aug.2, 1932 Flettner Feb. 11, 1936 Cable et aL. May 17, 1938 Focke July 20,1940 Young Sept. 22,1941 Martin June 22, 1943 Grace Jan. 15, 1946 LilleyDec. 9, 1947 Mount et a1 Sept. 6, 1949 Hunt Sept. 25, 1951 FOREIGNPATENTS Country Date Great Britain Jan. 31,1935 Great Britain Oct. 28,1935 Great Britain June 17, 1937 France Oct. 9, 1939

